KT-6646, KT-10482:

when a method (or a property getter) returns Nothing, emit
  ACONST_NULL
  ATHROW
after a call so that class files verifier knows that this is an exit point in a method.
Note that if an inline method returning Nothing throws an exception explicitly
(or via a chain of inline methods), this code will be deleted by DCE.

compiler/testData/codegen/box/controlStructures/returnsNothing/ifElse.kt

@@ -0,0 +1,14 @@
+var flag = true
+
+fun exit(): Nothing = null!!
+
+fun box(): String {
+    val a: String
+    if (flag) {
+        a = "OK"
+    }
+    else {
+        exit()
+    }
+    return a
+}

compiler/testData/codegen/box/controlStructures/returnsNothing/inlineMethod.kt

@@ -0,0 +1,12 @@
+inline fun exit(): Nothing = null!!
+
+fun box(): String {
+    val a: String
+    try {
+        a = "OK"
+    }
+    catch (e: Exception) {
+        exit()
+    }
+    return a
+}

compiler/testData/codegen/box/controlStructures/returnsNothing/propertyGetter.kt

@@ -0,0 +1,16 @@
+var flag = true
+
+object Test {
+    val magic: Nothing get() = null!!
+}
+
+fun box(): String {
+    val a: String
+    if (flag) {
+        a = "OK"
+    }
+    else {
+        Test.magic
+    }
+    return a
+}

compiler/testData/codegen/box/controlStructures/returnsNothing/tryCatch.kt

@@ -0,0 +1,12 @@
+fun exit(): Nothing = null!!
+
+fun box(): String {
+    val a: String
+    try {
+        a = "OK"
+    }
+    catch (e: Exception) {
+        exit()
+    }
+    return a
+}

compiler/testData/codegen/box/controlStructures/returnsNothing/when.kt

@@ -0,0 +1,14 @@
+fun exit(): Nothing = null!!
+
+var x = 0
+
+fun box(): String {
+    val a: String
+    when (x) {
+        0 -> a = "OK"
+        1 -> a = "???"
+        2 -> exit()
+        else -> exit()
+    }
+    return a
+}

compiler/testData/codegen/bytecodeText/inline/inlineReturnsNothing1.kt

@@ -0,0 +1,16 @@
+// NB '!!' uses Intrinsics.throwNpe()
+inline fun exit(): Nothing = null!!
+
+fun box(): String {
+    val a: String
+    try {
+        a = "OK"
+    }
+    catch (e: Exception) {
+        exit()
+        // ATHROW
+    }
+    return a
+}
+
+// 1 ATHROW

compiler/testData/codegen/bytecodeText/inline/inlineReturnsNothing2.kt

@@ -0,0 +1,16 @@
+inline fun exit(): Nothing =
+        throw RuntimeException() // ATHROW
+
+fun box(): String {
+    val a: String
+    try {
+        a = "OK"
+    }
+    catch (e: Exception) {
+        exit() // ATHROW inlined
+        // no ATHROW (removed as dead code)
+    }
+    return a
+}
+
+// 2 ATHROW

compiler/testData/codegen/bytecodeText/inline/inlineReturnsNothing3.kt

@@ -0,0 +1,17 @@
+inline fun exit(): Nothing = null!!
+inline fun exita(): Nothing = exit() // ATHROW
+inline fun exitb(): Nothing = exita() // ATHROW
+inline fun exitc(): Nothing = exitb() // ATHROW
+
+fun box(): String {
+    val a: String
+    try {
+        a = "OK"
+    }
+    catch (e: Exception) {
+        exitc() // ATHROW
+    }
+    return a
+}
+
+// 4 ATHROW